For a civil engineering and construction material, a construction material including a tatami mat core material, a material for vehicles, and the like, the so-called sandwich structure in which a plastic foamed body is used as a light core material and high-strength face materials are laminated on both surfaces thereof, has been actively developed as a material instead of a woody board which has been conventionally used. For example, Japanese Unexamined Patent Publication No. 6-134913 (1994) describes a laminated product wherein a polypropylene foamed body sheet is sandwiched between glass fiber reinforced polypropylene type resin layers, and also describes, as a method for producing the same, a method of heating a glass fiber reinforced polypropylene layer to not less than the melting point thereof to be made into a melting state, stacking this with a surface of a foamed body sheet, adhering them to each other to melt the surface of the foamed body sheet with heat which the polypropylene layer has, thereby melting and adhering the two to each other, and subsequently cooling and solidifying the two so as to be integrated with each other.
The present inventors advanced the development of a sandwich structure as described above. As a result, the inventors suggested a composite lamination wherein a reinforcing face material made of a polyolefin resin drawn sheet drawn up 10 times or more is laminated on a polyolefin resin foamed body sheet (an example of a sheet-form core material having a density of 30 to 300 kg/m3) (Japanese Patent Application No. 2001-13553). This composite lamination has the following advantages as compared with the product described in Japanese Unexamined Patent Publication No. 6-134913 (1994):
Since no glass fiber is used, the lamination is friendly to working environment and friendly to use environment;
Since the material thereof is made only of the polyolefin resin, the lamination can be re-melted or re-worked and can be recycled; and
The composite lamination deforms plastically in a certain bending strain area, and the shape thereof is kept.
However, if the reinforcing face material is heated to the melting point thereof or higher in order to attempt the production of this composite lamination by the method described in Japanese Unexamined Patent Publication No. 6-134913 (1994), the drawn orientation of the molecules is lost since the reinforcing face material is made of the polyolefin resin drawn sheet. As a result, desired flexural-rigidity and linear expansion property cannot be obtained.
The laminating described above is usually controlled by laminating-pressure. However, the compression property of the foamed body varies dependently on laminating-temperature; therefore, it is necessary to change the laminating-pressure dependently on the temperature. Furthermore, a problem that the thickness of manufactured product is scattered arises.
In recent years, in the field of house design, attention has been paid to the so-called barrier-free housing, wherein no step is present between a Japanese-style room and a Western-style room, as housing of a compromise type between Japanese and Western styles. However, conventional tatami mats (thick tatami mats) used in Japanese-style rooms have a thickness of approximately 55 mm; therefore, in order to remove a step between a Japanese-style room and a Western-style room using flooring materials for western-style rooms, the main current thickness of which is from approximately 5 to 20 mm, it is necessary to take measures in construction work, for example, lower the ground-beam sleeper of the Japanese-style room or increase the bulk of a floor bed of the Western room. Thus, a problem that construction work becomes much complicated is involved.
In order to cope with the above-mentioned problem, in recent years thin tatami mats having a thickness of approximately 7 to 25 mm have been commercially available instead of the conventional thick tatami mats. The thin tatami mats have advantages that application thereof is easy and exchange between a Japanese-style room and a Western-style room can easily be performed.
The performance required for the tatami mat material for thin tatami mats is that the material has flexural-rigidity even if the material is thin, and the linear expansion coefficient thereof is as small as possible. Specifically, as described in the specification of Japanese Patent Application No. 13-33990 (2001), a tatami mat core material made of a laminated composite satisfying the above-mentioned requirements can be produced by laminating a sheet, for a face material, made of a polyolefin resin drawn sheet having a linear expansion coefficient of 5×10−5 (1/° C.) or less on at least one face of a core material made of a polyolefin foamed body sheet in which cells extend in a spindle form in the thickness direction.
In order to exhibit the performance of the above-mentioned laminated composite at maximum, it is preferred to cross sheets for a face material which laminate on a surface of a core material (C) in the longitudinal direction and in the lateral direction, as illustrated in FIG. 4. This is because the face material is composed of longitudinal sheets (S1) and lateral sheets (S2) in an orthogonal form in this way, whereby anisotropy in the longitudinal direction and the lateral direction is cancelled.
In order to laminate sheets for a face material, in a longitudinally and laterally orthogonal-form, beforehand on a core material, it has been necessary in the conventional art to set longitudinal sheets and lateral sheets in an orthogonal form on a surface of the core material and then thermally melt and adhere them with a press or bond them with an adhesive agent. In this method, however, the operation for producing the lamination is intermittent; therefore, the speed of the production is small and a large amount of scrap material is generated and production efficiency is low, thereby resulting in high costs.
In light of the problems in the conventional art, an object of the present invention is to provide a method for producing a composite lamination using no inorganic fiber such as glass fiber without damaging the performance of a polyolefin resin drawn sheet and with a high thickness precision.
In light of the problems in the conventional art, another object of the present invention is to provide a device and a method which make it possible to continuously perform an operation for laminating sheets, for a face material, in a longitudinally and laterally orthogonal form on a core material and to produce a tatami core material made of a laminated composite with a high production efficiency.